Tree shelters were originally developed to prevent biotic stress caused by mammalian herbivory. This was accomplished by enclosing the seedling in a protective tube open at both ends to allow root and shoot growth. The height of the tube was a function of the stature of the herbivore. For example, 600-mm is considered adequate protection against rabbit browsing while 1200- to 1500-mm height tubes are generally prescribed to prevent deer browsing.
Tree shelters are a sub-category of what is referred to herein as “grow tubes.” A grow tube is a plant growth device that facilitates and promotes rapid and permanent establishment of the resident plant, even where mammalian herbivory is not a factor. In horticultural systems plant survival is generally not as high as in the wild, but there is still benefit to some level of protection. Additional benefit of a grow tube is to hasten and lower the cost of plant establishment. In a wild setting the first purpose is to ensure survival. But even in the wild setting, a component of plant establishment is to outgrow competing vegetation for nutrients, water and sunlight. Hence, rapid growth is generally considered advantageous whether in a horticultural or a wild setting.
Thermoformed grow tubes are known to provide the advantages of a structure that possesses both columnar and radial strength while consuming less material than either extruded or molded grow tubes. However, stock forms for thermoformed grow tubes tend to be more bulky and thus more costly to ship than extruded and certain molded stock forms. Also, the resilience of the thermoformed materials is known to exacerbate the problems of stem abrasion because of the hard or sharp edges that define the mouth of the tubes.
A thermoformed grow tube that addresses these various disadvantages would be a welcome addition to the horticultural and agricultural industries.